There are any number of pie-in-the-sky pundits who will tell you when a computer starts to get slow, to format the hard drive, reinstall Windows, and go on your merry way.

Unfortunately it’s not always realistic. I don’t clean up PCs all that often anymore, but here’s what I do when I need to.

First, I booted off a couple of antivirus live CDs and scanned the system. Neither found anything. I don’t have a favorite antivirus live CD anymore, and this is why. Sometimes you get lucky and one of these discs finds the biggest problem, and sometimes you don’t.

Next I ran Hijackthis, which found a number of browser toolbars. I got those gone, along with some other suspicious stuff, and the PC was better, but still not perfect. Search engines started working again, which was good, but websites tended to get extra ads injected and at one point a rogue download took over the system and I had to hard-power it down. Conventional antivirus wasn’t finding everything.

So I ran Malwarebytes, which found a half dozen or so remnants that Hijackthis hadn’t gotten rid of. Actually it claimed to find 616 items, but they were all traces of about a half dozen items. I ended up having to run Malwarebytes a second time after reboot.

I also let Windows Update run. Some of the malware was interfering with Windows Update, so the machine was about four months behind. That’s never good.

To keep things clean, I installed uBlock in Chrome, which blocks a lot of malware sites and malicious download links as well as ads–online advertising is a topic I’ll cover another day–and Secunia PSI, to keep critical non-Microsoft software up to date. I also installed and ran Mydefrag, because the drive was so fragmented that Windows’ built-in defragmenter didn’t know where to start.

Now, in an ideal world, I would format and reinstall because where there’s known malware, there’s likely to be traces of undiscovered malware. My friend and I will talk about that, but in the meantime, his wife’s computer is usable now.